The objective of the proposed study is to investigate aspects of sensory and perceptual functions in a large group of autistic individuals by means of brainstem and cortical auditory evoked responses (BAER and AER), autonomic reactivity (heart rate and skin conductance), and patterns of visual fixation. BAER and AER will be obtained in response to clicks. Autonomic reactivity will be measured in response to simple sensory stimulation of auditory, visual, tactile, thermal, and olfactory modalities; to complex verbal and social stimuli; and to a whirling object. Patterns of visual fixation will be obtained to pictures of simple geometrical figures, objects, faces, and to a moving target. Several issues will be examined. One is the comparison of autistic individuals with nonautistic retarded and normal subjects. A second issue concerns the problem of developmental delay as indicated by changes in autistic response patterns with age. Third is the relationship of the responses to prominent autistic symptoms such as speech and language abnormalities, modality preference, social responsiveness, and eye contact. Fourth is an attempt to identify autistic subgroups on the basis of response patterns. Finally, the data will be related to abnormalities revealed by CT scan and neurological examination. The ultimate goal of the present study is to clarify the role of sensory and perceptual defects in the development of other autistic behaviors, with the long term possibility of identifying structural abnormalities and allowing the development of appropriate training strategies.